README.md

01-Arrays

Topics Covered

• Prefix Sum
• Kadane Algorithm
• Two Pointer
• Sliding Window
• Sorting
• Greedy

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Problems List

No.	Problem	Difficulty	Topics	Link
1	Two Sum	Easy	Hashing, Array	Open
2	Best Time to Buy and Sell Stock	Easy	Greedy, Kadane	Open
3	Contains Duplicate	Easy	Hash Table	Open
4	Maximum Subarray	Easy	Kadane Algorithm	Open
5	Merge Sorted Array	Easy	Two Pointer, In-place	Open
6	Move Zeroes	Easy	Two Pointer, In-place	Open
7	Remove Duplicates from Sorted Array	Easy	Two Pointer	Open
8	Rotate Array	Easy	Array manipulation, Reverse	Open
9	Majority Element	Easy	Boyer-Moore Voting	Open
10	Missing Number	Easy	Math, XOR	Open
11	Intersection of Two Arrays	Easy	Hash Table, Two Pointer (sorted)	Open
12	Pascal Triangle	Easy	Dynamic Programming	Open
13	Meeting Rooms	Easy	Intervals, Sorting	Open
14	Rearrange Array Elements by Sign	Easy	Two Pointer, In-place	Open
15	Leaders in an Array	Easy	Suffix Max	Open
16	Rearrange Array Alternately	Easy	Two Pointer, Sorting	Open
17	Peak Index in Mountain Array	Easy	Binary Search / Linear Scan	Open
18	Minimum Moves to Equal Array	Easy	Math	Open
19	Pair Sum in Sorted Array	Easy	Two Pointer	Open
20	Product of Array Except Self	Medium	Prefix Products	Open
21	Maximum Product Subarray	Medium	Dynamic Programming	Open
22	Find Minimum in Rotated Sorted Array	Medium	Binary Search	Open
23	Search in Rotated Sorted Array	Medium	Binary Search	Open
24	3Sum	Medium	Sorting, Two Pointer	Open
25	Container With Most Water	Medium	Two Pointer	Open
26	Sort Colors	Medium	Dutch National Flag, Two Pointer	Open
27	Next Permutation	Medium	Array manipulation, Math	Open
28	Spiral Matrix	Medium	Simulation, Matrix traversal	Open
29	Set Matrix Zeroes	Medium	Matrix, In-place markers	Open
30	Merge Intervals	Medium	Intervals, Sorting	Open
31	Insert Interval	Medium	Intervals, Sorting	Open
32	Non-overlapping Intervals	Medium	Intervals, Greedy	Open
33	Meeting Rooms II	Medium	Intervals, Min-Heap	Open
34	Minimum Number of Arrows to Burst Balloons	Medium	Greedy, Intervals	Open
35	Gas Station	Medium	Greedy, Circular array	Open
36	Candy	Medium	Greedy, Two-pass	Open
37	Jump Game	Medium	Greedy	Open
38	Jump Game II	Medium	Greedy / BFS	Open
39	H-Index	Medium	Sorting, Binary Search	Open
40	Find All Duplicates in an Array	Medium	Index Marking	Open
41	Find Duplicate Number	Medium	Cycle Detection (Floyd), Binary Search on value range	Open
42	Maximum Sum Circular Subarray	Medium	Kadane Variation	Open
43	Subarray Product Less Than K	Medium	Sliding Window	Open
44	Minimum Swaps to Group All 1s	Medium	Sliding Window	Open
45	Equilibrium Index	Medium	Prefix Sum	Open
46	Stock Span Problem	Medium	Stack	Open
47	Chocolate Distribution Problem	Medium	Sorting, Sliding Window	Open
48	Longest Mountain in Array	Medium	Two Pointer	Open
49	Majority Element II	Medium	Boyer-Moore Generalized	Open
50	Array Nesting	Medium	Visited / DFS	Open
51	Global and Local Inversions	Medium	Permutation and properties	Open
52	Maximum Points from Cards	Medium	Sliding Window	Open
53	Maximum Width Ramp	Medium	Monotonic Stack / Deque	Open
54	Partition Labels	Medium	Greedy, Intervals	Open
55	Trapping Rain Water	Hard	Two Pointer, Stack	Open
56	First Missing Positive	Hard	Index Marking	Open
57	Longest Consecutive Sequence	Hard	HashSet, Union-Find	Open

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Important Patterns

Two Pointer

• Two Sum II
• Container With Most Water
• 3Sum

Kadane Algorithm

• Maximum Subarray
• Maximum Circular Subarray

Prefix Sum

• Subarray Sum Equals K
• Pivot Index

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Notes and links to problem solutions can be added below.